The method of heating and cooling non-hardened and tempered steel and equipment thereof
The method and the equipment thereof of a kind of heating and cooling non-hardened and tempered steel of the present invention.A kind of like this method and apparatus of heating and cooling non-hardened and tempered steel particularly, the speed of cooling of its forging after by the control forge hot, and do not need additional heat treatment structure refinement technology, just can realize that non-hardened and tempered steel has the equally high desirable strength of quenched and tempered steel.
For promoting the intensity and the toughness of machine parts, carry out structure refinement thermal treatment usually.From 1970's, since twice oil crisis in the world, industrial advanced country trends towards developing energy-conservation steel as leading indicator.In recent years, because oil price rises and requirement on environmental protection, world's All Countries is all profoundly experienced the necessity of the energy-conservation steel of development.
In table 1, provided the manufacturing processed of forging.
|A: quenched and tempered steel ||Cutting stock → heating → forging → finishing cleaning → → air cooling → normalizing → heat-treated sturcture refinement → processing |
|B: non-hardened and tempered steel ||Cutting stock → heating → forging → finishing cleaning → controlled chilling → processing |
As described in Table 1, technology A is a process of making the raw material production forging with quenched and tempered steel.Technology B makes the process that raw material generates forging with non-hardened and tempered steel.
The thermal treatment process of carbon quenched and tempered steel during Fig. 1 represents, but do not express its forging process and normalizing process, the forging process and the technology for controlled cooling of carbon non-hardened and tempered steel during Fig. 2 A represents.
There are more following advantages in the manufacturing process of non-hardened and tempered steel forging:
At first, owing to do not need structure refinement thermal treatment after the forging cooling, can eliminate expending that structure refinement thermal treatment brings, and shorten the time that forging is produced.
The second owing to after the forging cooling, do not need it is carried out structure refinement thermal treatment, needn't burning petroleum or consume electric power produce above-mentioned institute energy requirement.Thereby, reduced environmental pollutant such as SO
The 3rd, owing to controlling Heating temperature or cooling temperature, thereby reduced the bum origin cause of formation such as decarburization, and then reduced with low quality in order to forge non-hardened and tempered steel.
At last, this technology can be eliminated the phase transformation that the non-equilibrium cooling in the hot forging process causes and the influence of unrelieved stress.
Although non-hardened and tempered steel has above-mentioned advantage, non-hardened and tempered steel is not commonly used for the forging raw material.In other words, owing to utilize existing forging process and forging equipment, can not obtain quality identical or mechanical property such as high tenacity, and the non-hardened and tempered steel that is of little use is as the forging raw material with quenched and tempered steel.
Day patent application No.55-158218 of the present disclosure discloses the technology of carbon non-hardened and tempered steel manufacturing bent axle in a kind of the forging.Yet this patent application has only been announced with the method for the speed cooling non-hardened and tempered steel of 50 ℃/min, and do not announce the concrete grammar that forges non-hardened and tempered steel.
In addition, a day patent application No.58-177414 of the present disclosure discloses a kind of concrete equipment that forges non-hardened and tempered steel.The somewhere is installed with and is used to spray water or jet many forks nozzle sending the travelling belt of fortune non-hardened and tempered steel spare in this equipment above.Yet aforesaid device does not comprise based on the device from the controlled chilling speed of the temperature value of arithmetical unit.Thereby equipment operator is come controlled chilling speed by measuring the speed of adjusting conveyer through the temperature of the forging of adjustable cooling room.Therefore, the response speed of equipment is slow.And if forging temperature inequality, then cooling rate just changes in the cooling room.
In 700 ℃～1000 ℃ temperature ranges, the cooling rate linear change of non-hardened and tempered steel, and certain speed of cooling is arranged.The rate of cooling of carbon non-hardened and tempered steel during Fig. 2 B represents.
With reference to Fig. 2 B, in 700 ℃～600 ℃ temperature ranges, non-hardened and tempered steel undergoes phase transition.Thereby the thermal conductivity of non-hardened and tempered steel changes, and correspondingly its rate of cooling changes.And because in the non-hardened and tempered steel process of cooling, latent heat of phase change discharges, the temperature of non-hardened and tempered steel can raise.
Day, patent application No.2-209419 of the present disclosure disclosed a kind of method, can address the above problem.In this patent application, temperature sensor all has been installed in the import and the outlet of cooling room.And be the control exhaust air rate, central processing unit receives the temperature sensor signal that temperature sensor produces, and sends instruction to fan electromotor., motor revolution (RPM) must just can be controlled based on the difference of measuring temperature and design temperature apart between the about 200-300mm of cooling piece in the temperature sensor installation site.As a result, temperature sensor is exposed under the high temperature, has shortened its life-span.
Simultaneously, the disclosed present patent application No.4-276010 of Japan discloses a kind of forging adaptive technique, even this method is not measured the temperature of forging in transmission, also can accurately control the cooling rate after the forging.According to this invention, determine best cold air stream speed by the temperature of utilizing the thermometer measure forging, thereby 900 ℃～600 ℃ scope inner control cooling rates.
As a result, can obtain to satisfy the best exhaust air rate that above-mentioned cooling rate requires.Yet above-mentioned this forging adaptive technique can only be used to keep determining the production line of productivity.In this production line, there is no need to measure the temperature of forging.
The present invention designs for addressing the above problem.Its purpose just provides a kind of method of non-hardened and tempered steel heating and cooling, the cooling rate of this method after by control forging forge hot, and, just can make non-hardened and tempered steel have the same high desirable strength with quenched and tempered steel without the thermal treatment of additional tissue refinement.
Another object of the present invention provides a kind of equipment of heating and cooling non-hardened and tempered steel, and it can be by the cooling rate after the control forging forge hot, and need not additional structure refinement thermal treatment, makes non-hardened and tempered steel have the same high desirable strength with quenched and tempered steel.
For achieving the above object, the invention provides a kind of method of heating and cooling non-hardened and tempered steel, step comprises:
(S1) in process furnace, under the temperature in 1150 ℃ to 1300 ℃ temperature ranges, the heating non-hardened and tempered steel; To the non-hardened and tempered steel forge hot to produce forging;
(S2) utilizing travelling belt forging to be sent in the process of cooling room, the forging temperature is controlled at below 1000 ℃;
(S3) forging is cooling off under the following state: at forging through in the process of cooling room, for the thermograde that keeps forging in the temperature gradient of setting, by the cooling of central processing unit control forging.
And, for reaching above-mentioned second purpose, the invention provides a kind of equipment of heating and cooling non-hardened and tempered steel, this equipment comprises:
A process furnace that has temperature sensor, this temperature sensor are used for measuring the forging temperature at furnace outlet;
A cooling room, it comprises an import, an outlet, one is installed in the cooling-part on cooling room top, and is installed in some temperature sensors in the cooling room, and wherein the cooling room entrance width is greater than the width of outlet;
A central processing unit is by accepting the signal from temperature sensor, controlled chilling parts.
In conjunction with the drawings, to the detailed description of a preferred embodiment of the present invention, above-mentioned purpose of the present invention and other characteristics, advantage all will become very clear, in the accompanying drawing:
The thermal treatment process figure of carbon quenched and tempered steel during Fig. 1 represents does not wherein provide thermal forging technology and normalizing process;
The forging process of carbon non-hardened and tempered steel and technology for controlled cooling figure during Fig. 2 A represents;
The rate of cooling figure of carbon non-hardened and tempered steel during Fig. 2 B represents;
Fig. 3 is according to carbon non-hardened and tempered steel heating and cooling equipment synoptic diagram in of the present invention;
Fig. 4 is the schema of middle carbon non-hardened and tempered steel heating and cooling method and apparatus control system thereof.
Below, with reference to accompanying drawing, describe the preferred embodiments of the present invention in detail.
For using oil combustion, the heating non-hardened and tempered steel is necessary to be provided with the fuel tap of stepless control oil mass and the control device of control fuel tap.Because the development of precision optical machinery or electronic component, the above-mentioned control oil system that is made of fuel tap and fuel tap control device are easy to realize.In the control oil system, central processing unit, received signal such as electric power, these signals are by the light thermometer such as fibre optic thermometer or the infrared thermometer generation that are installed in the process furnace.Then, central processing unit sends instruction to the fuel tap control device, and control device can keep in the stove temperature in temperature required scope like this.
When with electrical heater non-hardened and tempered steel being heated, power input in the stove and temperature are easy to by amperometer or power meter control.In addition, when with induction heater non-hardened and tempered steel being heated, power input in the stove and temperature are controlled by the following parameter of appropriate control: the frequency of high frequency or low frequency, the external diameter difference of internal coil diameter and non-hardened and tempered steel, size of current, voltage swing, the feeding speed of non-hardened and tempered steel.
In described Controlling System, will forged steel at process furnace, be heated to 1150 ℃ to 1300 ℃ scope, preferably the steel temperature is between 1200 ℃～1250 ℃.If Heating temperature is higher than 1300 ℃, the crystal grain of non-hardened and tempered steel is grown up fast, the result, and the toughness of final forging worsens, and serious decarburization takes place.Carry out forge hot if not the quenched and tempered steel Heating temperature is lower than 1150 ℃, then the hot workability of steel worsens.Thereby, being shaped for making steel, excessive load is added on the metal die, or crackle can occur in forging.
In the heat-processed, non-hardened and tempered steel heats with two process furnace, or adopts two step heating processes.In two step heating processes, carry out preheating (the first step) earlier, enter the main heating phase again (second step).
Thereby, can solve steel inside and be heated to forging temperature, and steel surface problem overbumt., except heavy parts or the low part of thermal conductivity, all available single step heating process of most of steel parts.When forging bar heated in process furnace, its temperature was lower than temperature in the stove, and this is that it self thermal conductivity and volume size causes.Thereby, if the operator based on temperature survey forging bar temperature in the stove, can produce measured deviation.
Fig. 3 is the equipment synoptic diagram according to carbon non-hardened and tempered steel in the heating and cooling of the present invention.With reference to Fig. 3, the forging temperature is by the thermometer measure that is installed in contiguous furnace outlet.Central processing unit 20 receives the temperature value of being measured by thermometer, and sends instruction to control device as fuel tap or the amperometer of controlling the forging Heating temperature.In other words, for reaching the temperature that needs, realize by central processing unit 20 control fuel taps or amperometer.
In the past, because the existence of gas in the stove, the thermometer transducing part is the energy measurement precise temp not.Yet, can survey precise temp by using infrared thermometer now.
Below, the method for description control forging speed of cooling.
According to the temperature of non-hardened and tempered steel forging 3, determine the distance interval between travelling belt and cooling room 10 imports, and the speed that transmits.That is after forge hot the temperature of forging 3, forging 3 through travelling belt 2 when arriving at cooling room 10, remain on below 1000 ℃.Because for keeping existing rate of cooling in the process of cooling, the temperature that enters the forging 3 of cooling room 10 must keep even.
And, the cooling room 10 because forging 3 is at high temperature packed into, forging 3 does not draw off from cooling room 10 under the uncompleted state of phase transformation.Thereby, can obtain the mechanical property that needs.
Below forging 3 phase point temperatures, must cool off fully, then, carry out air cooling.Alloy phase height temperature is according to alloying constituent, heat-treat condition and speed of cooling and change.Best, the temperature eventually in the process of cooling is directly measured the forging temperature by the job site and is determined.
As the non-modified carbon steel of machine parts, must be fine grain structure.And, need the precipitation of control precipitation hardening phase to separate out condition for producing required forging.If can not satisfy above-mentioned required condition, can not obtain forging with excellent in toughness and intensity.
Through in the cooling room 10, be contained in the thermometer of cooling room 10 ingresss at forging 3, measure the surface temperature of forging 3, and send its observed value to central processing unit 20.Then, central processing unit deducts the temperature value that is contained in forging that thermometer is surveyed 3 surfaces, cooling room 10 exit from above-mentioned observed value; Remove The above results with the time period of stay of forging 3 in cooling room 10 subsequently.At this moment, in the timed interval, utilize of the translational speed acquisition of the length of cooling room 10 divided by travelling belt 2.Cooling room 10 length are determined according to the needs of equipment.
Although the translational speed of travelling belt 1 changes, can consider that to like products productivity keeps a translational speed.As a result, by the operation stdn, can determine fixedly translational speed for the travelling belt 1 of each product.
If with the fixed speed cooling room 10 of packing into, the thermometer that is installed in cooling room 10 imports and outlet is measured the temperature of forging 3 respectively to forging 3, and sends its measured temperature to central processing unit 20 by travelling belt 1.Then, central processing unit 20 calculates thermograde according to measured temperature.If the thermograde that is calculated by central processing unit 20 and the thermograde difference of setting are higher than 30%, central processing unit 20 will issue instructions to each motor, and blowing fan 8 and exhaust fan 5 are quickened or slow down.
If forging 3 cooling room 10 of not packing into, be installed in the thermometer 9 of cooling room 10 ingresss, in the timed interval is higher than 2 minutes scope, for being lower than a specified temp of 500 ℃.Thereby through deducting on cooling room 10 required times in 2 minutes the specified time interval, central processing unit 20 sends instruction to fan electromotor, makes blowing fan and exhaust fan stop working at forging.
Freezing air by blowing fan 8 is sent into cools off the forging 3 of packing into through cooling room 10 inlets.At this moment, air themperature raises, and volume increases.As a result, density of air reduces, thereby air rises.Because the top board height of cooling room 10 ingresss is lower than the top board height of cooling room 10 outlets, the air that heats up in cooling forging 3 is discharged cooling room 10 smoothly.Therefore, new freezing air can enter cooling room 10.And, can prevent the inhomogeneous cooling of forging 3 by in cooling room 10, producing eddy current.
In view of the internal structure of cooling room 10, when blowing fan 8 or exhaust fan 5 work, air can flow to outlet from cooling room 10 imports naturally.When the speed of cooling to forging 3 requires to be higher than its air cooling speed, need to quicken air flowing.Thereby, for obtaining required speed of cooling, must open blowing fan 8 and exhaust fan 5 simultaneously.
Air supply pipe 7 is installed on the cooling room inner top.Some are used for being installed in to the air nozzle of forging 3 injection airs the bottom of air supply pipe 7.The arrangement of air nozzle 11 layout that is inclined upwardly from the import of cooling room 10 to outlet.Like this, from the air cooling forging 3 of air nozzle 11 ejections, and the air spontaneous current of heating is to the outlet of cooling room 10.
One or more devices as vapor pipe 6 are installed on cooling room 10 top boards along long axis direction, and wherein vapor pipe 6 has big internal diameter, and they constitute the part of air supply pipe 7.In addition, can use main pipe line and the small transfer line that has many jet holes, they are connected with each other, as backbone and the rib of animal.If main pipe line and small transfer line are used as air supply pipe 7, can cool off forging 3 from different directions, and forging 3 each several parts are evenly cooled off.At this moment, jet hole can be positioned at the small transfer line long axis direction or vertical direction cuts part formation, or constitutes with the aperture form.For making air slowly flow to the outlet of cooling room 10, air nozzle 11 spray angles are preferably 45 degree between 10～80 degree, be sprayed onto on the forging 3.For evenly cooling off the forging 3 that moves at travelling belt 1, air must evenly flow in cooling room 10.Then, can be easily in the rate of cooling of controlling forging 3.Yet when spray angle is lower than 10 degree or is higher than 80 when spending, air can not flow smoothly.
Usually, the cooling rate that obtains in air of middle carbon non-hardened and tempered steel is different because of forging 3 sizes., if not the weight of quenched and tempered steel is 1 to 20kg, then cooling rate is 30～80 ℃/min.
Different according to power of motor with the size of forging 3, change with the acceleration refrigerative cooling rate of forcing air draft to obtain., the cooling rate of non-hardened and tempered steel needs is 50 ℃～160 ℃/min.When making raw material with low-carbon bainite series non-hardened and tempered steel, cooling rate must reach 120～150 ℃/min, just is applicable to this half quenching technology.In this case, must additional cooling supply-pipe be installed near air supply pipe 7, be used for water spray or spraying.
Simultaneously, since the steam in the cooling room 10, thermometer 4,9, and 12 can make mistakes in measurement.In recent years, a kind of thermometer that grows up can address the above problem.During with light sensor measurement temperature, need an additional air supply pipe be installed, be used to eliminate measuring error at contiguous temperature sensor place.By being installed, air supply pipe can eliminate gas-bearing formation between temperature sensor and forging 3.
According to the present invention, for controlling cooling rate equably, the additional temp meter is installed in cooling room 10 imports and exit separation from the desired location for 1/10 to 1/3 zone of benchmark.According to the thermal gradient of desired location, controlled chilling speed.Therefore, controlled chilling speed so effectively.
With distance between cooling room 10 imports and the outlet is benchmark, and the desired location in its zone of 1/10 to 1/3 must be installed internal temperature sensor 12.Because rate of cooling linear change in each zone, thereby can obtain to be suitable for controlling the accurate data of cooling rate.
If internal temperature sensor 12 is contained in above-mentioned each regional somewhere, the place ahead, thermograde is then little and change fast.If internal temperature sensor 12 is installed in above-mentioned each regional somewhere, rear, then cooling rate changes formation one curve.Particularly owing to the phase transformation of forging 3, in 625 ℃～700 ℃ temperature ranges, cooling rate changes irregular.At last, if be benchmark with distance between the outlet of cooling room 10 and the import, internal temperature sensor 12 is installed in its rear position, 2/3 place, and cooling rate changes slowly, and little along the miles of relative movement thermal gradient.
When thermograde long when cooling room 10 length or that set is low, need between the import of cooling room 10 and outlet, adorn some thermometers everywhere.Then, can accurately control cooling rate.
Quicken the blowing fan 8 and the exhaust fan 5 of cooling usefulness, be installed in the import and the exit of cooling room 10 respectively, drive by direct-current machine.Thereby, can easily control the actuating speed of blowing fan 8 and exhaust fan 5, and response speed is fast.
Because have insulation in cooling room 10 locular walls, the heat of cooling room can not pass on the workpiece.Thereby Working environment can not worsen, and can carry out controlled chilling to slow cooling forging 3.Herein, thermal insulator is selected from the group that is made up of asbestos, mica, pottery and some other thermal insulation materials.
When using constant speed motor or compressor to supply air to cooling room, a control valve can be installed be used for controlling flow velocity, thus controlled chilling speed.Wherein control valve is installed in certain position of motor or compressor and air supply pipe 7 connection portions.Present method is suitable for the controlled chilling to forging 3 slow cooling.
Hereinafter will describe an example of the present invention in detail.
In the part of the crawler belt of a heavy device, the running roller at this heavy device of crawler belt upper support is made like this: the housing that two forgings form through forge and machining after, the intermediate portion is welded.At this moment, make the forge piece of a 17kg non-hardened and tempered steel rather than quenched and tempered steel.The Heating temperature of forge piece remains in 1200～1250 ℃ of scopes, and temperature remains on 1390～1400 ℃ in the corresponding stove.After forging processing, the Heating temperature of forging remains in 900～500 ℃ the temperature range.
Fig. 4 is the schema of carbon non-hardened and tempered steel heating and cooling method and apparatus control system thereof in the expression.
|Sequence number ||Temperature in the stove (℃) ||Final forging temperature (℃) ||The cleaning end temp (℃) ||950-500 ℃ of cooling rate (℃/min) ||Cooling rate change temperature (℃) ||Steel constituent (wt%) |
| ??1 || ?1390～ ?1400 || ??1230 || ??1094 || ????79 || ????665 || ??C?0.38，Si?0.23， ??Mn?1.32，P?0.015， ??S?0.024，V?0.105， ??A?l0.028，N ??0.0103， ??Mo?0.02，Ti?0.01 |
| ??2 || ??1161 || ??1042 || ????64 || ????660 |
| ??3 || ??1195 || ??1050 || ????74 || ????670 |
| || || || || |
As shown in table 2, when central carbon non-hardened and tempered steel cools off in forcing air draft, about 60～80 ℃/min of cooling rate.At this moment, the metal final structure is ferrite+perlite, and its grain fineness number is 5 grades to 6 grades in the ASTM standard.
If middle carbon non-hardened and tempered steel air cooling, its cooling rate is 37～41 ℃/min.Final acquisition metal construction is ferrite+perlite, and its grain fineness number is 1 to 3 grade in the ASTM standard.At this moment, the ferritic phase volume fraction is lower than the situation in the above-mentioned steel, and it is thick that crystal grain becomes.
If a large amount of non-hardened and tempered steels are with common forging process processing, the same manner cools off, and cooling rate is lower than above-mentioned value.
Difference has increased between cooling rate and the above-mentioned value.The thickness of considering steel part is 50mm, and this result and " thermal treatment " magazine Vol.20 that is published by Japanese thermal treatment engineering association, No.7 announce and come to the same thing.By this publication, when the non-hardened and tempered steel diameter was 20mm, cooling rate was 80 ℃/min, and when the non-hardened and tempered steel diameter was 40mm, cooling rate was 44 ℃/min, and when the non-hardened and tempered steel diameter was 70mm, cooling rate was 27 ℃/min.
When forging was cooled off by water spray, cooling rate reached 150～174 ℃/min.When with boiling water cooling forging, cooling rate is between 105～129 ℃/min.At this moment, on the surface that cooling rate increases, upper bainite and lower bainite coexistence.In the depths, constitute mixed structure by upper bainite and " ferrite+perlite ".This moment, cooling rate increased, and the amount of bainite increases.
Thereby, according to water temperature, mist and air ratio, the injection pressure and the air flow quantity of mist are controlled the technology of spray cooling non-hardened and tempered steel easily.Although, under similarity condition, cool off forging, the forging cooling rate changes.Because have phase transformation in the forging process of cooling.
According to the present invention, the phase transformation of non-hardened and tempered steel occurs in 700 ℃ to 625 ℃.In this temperature range, austenitic transformation is ferrite and perlite.
If with the cooling of above-mentioned process for cooling, then the forging die temperature is low in cooling room 10 for forging, and forging is after clearing up, non-uniform temperature.Thereby, fail under the temperature condition that obtains desired physical properties, to cool off.For addressing this problem, forging reheats in 900～950 ℃ of temperature.
Subsequently, forging cools off, thereby can obtain the physicals of needs.
The temperature on forging surface is by the thermometer measure that is installed in cooling room 10 exits.Thermometric temperature value sends central processing unit 20 to.Then, central processing unit 20 with by the observed value that is installed in cooling room ingress thermometer, calculates this value.Then, central processing unit 20 judges whether thermograde is suitable in the cooling room 10, and sends control signal to motor.
As mentioned above, in the method and equipment thereof of heating and cooling non-hardened and tempered steel of the present invention, the measurement of forging temperature is measured simultaneously in cooling room 10 imports and exit in the cooling room 10.Thereby, can accurately control motor and keep the uniform temperature gradient.Thereby, the forging with even performance can be provided.
The invention solves the grain growth that some problem such as burning cause, toughness reduces, surface decarburization, the strength difference (inhomogeneous) that is caused by inhomogeneous cooling and phase transformation.The solution of these problems is to realize by the heating and cooling process of controlling forging.And can reduce the required manufacturing expense of forging processing.In addition, can prevent the pollution of the environment, obtain even cooling rate.
Although the present invention has only described certain embodiments especially, should be understood that in the prerequisite that does not break away from claims institute's restricted portion of the present invention and spirit those skilled in the art make in form and details that to revise be possible.